/Engine/Plugins/Runtime/NetworkPrediction/Source/NetworkPrediction/Public/NetworkPredictionWorldManager.h
Returns unique ID for a new simulation instance regardless of type. Clients set bForClient to get a negative, temp ID to use until server version comes in
[FNetworkPredictionID](API\Plugins\NetworkPrediction\FNetworkPredictionID) CreateSimulationID ( const bool bForClient )